1. Field of the Invention
This invention relates to the field of suspensions for disk drives. More particularly, this invention relates to the field a microactuator for a suspension, the microactuator having a stacked d33 mode construction and a constraining layer.
2. Description of Related Art
Magnetic hard disk drives and other types of spinning media drives such as optical disk drives are well known. A typical disk drive unit, for example, is shown in FIG. 1 of U.S. Pat. No. 8,879,210 issued to Hahn et al. (“the Hahn '210 patent”) which is assigned to the present Applicant and which is incorporated by reference herein. The typical disk drive unit includes a spinning magnetic disk containing a pattern of magnetic storage medium ones and zeroes on it that constitutes the data stored on the disk drive. The magnetic disk is driven by a drive motor. The disk drive unit further includes a disk drive suspension to which a magnetic read/write is mounted proximate a distal end of load beam. The “proximal” end of a suspension or load beam is the end that is supported, i.e., the end nearest to the base plate which is swaged or otherwise mounted to an actuator arm. The “distal” end of a suspension or load beam is the end that is opposite the proximal end, i.e., the “distal” end is the cantilevered end.
The suspension is coupled to an actuator arm, which in turn is coupled to a voice coil motor that moves the suspension arcuately in order to position the head slider over the correct data track on the data disk. The head slider is carried on a gimbal which allows the slider to pitch and roll so that it follows the proper data track on the disk, allowing for such variations as vibrations of the disk, inertial events such as bumping, and irregularities in the disk's surface.
Both single stage actuated disk drive suspensions and dual stage actuated (DSA) suspension are known. In a single stage actuated suspension, only the voice coil motor moves the suspension.
In a DSA suspension a small actuator located on the suspension moves the head slider in order to position the head slider over the correct data track. The actuator provides both finer positioning of the head slider than does the voice coil motor, and provides higher servo bandwidth than does the voice coil motor. The actuator may be located in various places on the suspension depending on the particular DSA suspension design. Typically, left- and right-side actuators act in push-pull fashion to rotate the load beam or the distal end of the load beam. Some of the earliest DSA suspension designs placed the actuator on the baseplate, with actuation of the PZTs causing the entire load beam to rotate. Actuators used in DSA suspension have been called milliactuators or microactuators. Dual stage actuated (DSA) suspensions have become common in recent years as data track widths have continued to decrease.
A piezoelectric element is often used as the microactuator motor, although static electric microactuators and other types of microactuator motors have been proposed and used. A commonly used piezoelectric material is lead zirconate titanate (PZT), although other piezoelectric materials are also used and known. In the discussion and claims that follows, for simplicity the piezoelectric device that is the microactuator will sometimes be referred to simply as a “PZT” for shorthand, it being recognized that the piezoelectric material need not be lead zirconate titanate. Thus, as used herein the term “PZT” can refer to any piezoelectric material or any piezoelectric device formed of any piezoelectric material.
Other exemplary DSA suspensions are disclosed in U.S. Pat. No. 9,117,468 issued to Zhang et al., and U.S. Pat. No. 8,879,210 to Hahn et al., both of which are assigned to the assignee of the present application.
FIG. 1 is a top plan view of a prior art DSA suspension in which two PZTs are mounted near the gimbal, and act directly on the gimbal through flexible connectors. That suspension is similar to the suspension shown in the Hahn '210 patent. Such suspensions are sometimes called gimbal DSA suspensions, or simply GSA suspensions. A GSA suspension is one type of DSA suspension. In the figure, suspension 10 includes a flexure 20 which is mounted to load beam 12. Flexure 20 includes electrical circuit 22 which includes copper contact pad 24 which carries the PZT driving voltage, and copper contact pad 28 which is grounded. The PZTs 14 act on head slider 30 which is mounted to a gimbaled area of flexure 20 via thin ribbon-like flexible stainless steel connectors 26. One PZT expands while the other contracts, rotating head slider 30 slightly in order to position the magnetic transducers within slider 30 over the desired spot on disk platter 101 with precision.